Water Testing Results and Analysis
Our 2021 water testing season is now over and the results are in. Between May and September, FBSR samples local lakes, rivers, and streams to help determine water quality of the Big Sioux River Watershed. Each year, we collect roughly 500 samples, spanning over 100 miles from Dell Rapids to Akron, IA. Following processing from the South Dakota Health Lab, the results are included in the South Dakota DANR water quality portal and posted to our website to allow public access of our data. Testing parameters included E. coli, total suspended solids, and nitrates.
Overall, the story of this year's data is that water quality improves with lower flows. In general, 2021 results show:
Contaminant levels spiked following rainfall events; recreationists should avoid immersion recreation following heavy rainfall events.
Absent rainfall events, Lake Alvin, Lake Lakota, and Wall Lake, which FBSR tested, are performing well in clarity; however, Lake Alvin still suffers from E. coli contamination after heavy rainfall events which cause excessive runoff and the closure of its swimming beach.
Our rivers and streams are regularly exceeding safe levels for E. coli. More riparian buffers are needed to reduce the runoff of contaminants.
Water quality decreases in the Big Sioux River as it flows south. Overall the southern monitoring sites at Newton Hills and Akron have higher levels of sediment, E. Coli, and nitrates.
Nitrate levels continue to rise but are within safe levels at locations north of the Rock River confluence with levels rising after the RockRiver joins the Big Sioux.
The mean and median nitrate levels were lower in 2021 than 2020, likely due to drought conditions. However, this is the first year in the past three that nitrate exceeded safe levels in the Big Sioux River.
